`star` Microbes as Biocontrol Agents
`star` Agents used for Biocontrol
`star` Microbes as Bioffertilisers


● `color{Violet}"Biocontrol"` refers to the use of `color{Violet}"biological methods"` for controlling plant diseases and pests.

● In `color{Violet}"modern society"`, these problems have been `color{Violet}"tackled increasingly"` by the use of chemicals – by use of `color{Violet}"insecticides and pesticides"`.

● These chemicals are `color{Violet}"toxic"` and `color{Violet}"extremely harmful"`, to human beings and animals alike, and have been `color{Violet}"polluting our environment"` (soil, ground water), fruits, vegetables and crop plants.

● Our soil is also `color{Violet}"polluted"` through our use of `color{Violet}"weedicides"` to remove weeds.

● `color{Violet}"Biological control"` of pests and diseases: In `color{Violet}"agriculture"`, there is a method of controlling pests that relies on `color{Violet}"natural predation"` rather than introduced chemicals.

● A `color{Violet}"key belief"` of the organic farmer is that `color{Violet}"biodiversity furthers health"`.

● The more variety a `color{Violet}"landscape"` has, the more `color{Violet}"sustainable"` it is.

● The `color{Violet}"organic farmer"`, therefore, works to create a system where the `color{Violet}"insects"` that are sometimes called `color{Violet}"pests"` are not eradicated, but instead are kept at `color{Violet}"manageable levels"` by a complex system of `color{Violet}"checks and balances"` within a living and vibrant ecosystem.

● Contrary to the `color{Violet}"conventional farming practices"` which often use chemical methods to kill both `color{Violet}"useful and harmful life"` forms indiscriminately, this is a `color{Violet}"holistic approach"` that seeks to develop an understanding of the `color{Violet}"webs of interaction"` between the myriad of organisms that constitute the field `color{Violet}"fauna and flora"`.

● The `color{Violet}"organic farmer"` holds the view that the `color{Violet}"eradication"` of the creatures that are often described as `color{Violet}"pests"` is not only possible, but also `color{Violet}"undesirable"`, for without them the `color{Violet}"beneficial"` predatory and parasitic insects which depend upon them as food or hosts would `color{Violet}"not be able to survive"`.

● Thus, the use of `color{Violet}"biocontrol measures"` will greatly `color{Violet}"reduce our dependence"` on toxic chemicals and pesticides.

● An `color{Violet}"important part"` of the biological farming approach is to `color{Violet}"become familiar"` with the various life forms that inhabit the field, `color{Violet}"predators as well as pests"`, and also their life cycles, patterns of feeding and the habitats that they prefer.

● This will help develop `color{Violet}"appropriate means"` of biocontrol.


● The very familiar beetle with red and black markings – the `color{Violet}"Ladybird"`, and `color{Violet}"Dragonflies"` are useful to get rid of `color{Violet}"aphids and mosquitoes"`, respectively.

● An example of microbial biocontrol agents that can be introduced in order to control `color{Violet}"butterfly caterpillars"` is the bacteria `color{Violet}"𝘉𝘢𝘤𝘪𝘭𝘭𝘶𝘴 𝘵𝘩𝘶𝘳𝘪𝘯𝘨𝘪𝘦𝘯𝘴𝘪𝘴"` (often written as `color{Violet}"Bt"` ).

● These are available in `color{Violet}"sachets as dried spores"` which are mixed with water and sprayed onto `color{Violet}"vulnerable plants"` such as brassicas and fruit trees, where these are eaten by the `color{Violet}"insect larvae"`.

● In the gut of the larvae, the `color{Violet}"toxin is released"` and the `color{Violet}"larvae get killed"`.

● The bacterial disease will `color{Violet}"kill the caterpillars"`, but leave `color{Violet}"other insects unharmed"`.

● Because of the development of `color{Violet}"methods of genetic engineering"` in the last decade or so, the scientists have introduced B. 𝘵𝘩𝘶𝘳𝘪𝘯𝘨𝘪𝘦𝘯𝘴𝘪𝘴 toxin `color{Violet}"genes into plants"`.

● Such plants are `color{Violet}"resistant to attack"` by insect pests.

● `color{Violet}"Bt-cotton"` is one such example, which is being cultivated in `color{Violet}"some states"` of our country.

● A `color{Violet}"biological control"` being developed for use in the treatment of plant disease is the `color{Violet}"fungus 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢"`.

● 𝘛𝘳𝘪𝘤𝘩𝘰𝘥𝘦𝘳𝘮𝘢 species are `color{Violet}"free-living fungi"` that are very common in the `color{Violet}"root ecosystems"`.

● They are `color{Violet}"effective biocontrol agents"` of several plant pathogens.

● `color{Violet}"Baculoviruses"` are pathogens that `color{Violet}"attack insects"` and other arthropods.

● The majority of baculoviruses used as `color{Violet}"biological control agents"` are in the genus `color{Violet}"Nucleopolyhedrovirus"`.

● These viruses are excellent candidates for `color{Violet}"species-specific"`, `color{Violet}"narrow spectrum"` insecticidal applications.

● They have been shown to have `color{Violet}"no negative impacts"` on plants, mammals, birds, fish or even on non-target insects.

● This is especially desirable when `color{Violet}"beneficial insects"` are being `color{Violet}"conserved'"` to aid in an overall `color{Violet}"integrated pest management (IPM) programme"`, or when an ecologically sensitive area is being treated.


● With our present day life styles environmental `color{Violet}"pollution"` is a major `color{Violet}"cause of concern"`.

● The use of the `color{Violet}"chemical fertilisers"` to meet the ever-increasing demand of `color{Violet}"agricultural produce"` has contributed significantly to this pollution.

● Of course, we have now realised that there are problems associated with the `color{Violet}"overuse of chemical fertilisers"` and there is a large pressure to switch to `color{Violet}"organic farming"` – to use of `color{Violet}"biofertilisers"`.

● Biofertilisers are organisms that `color{Violet}"enrich the nutrient quality"` of the soil.

● The `color{Violet}"main sources"` of biofertilisers are `color{Violet}"bacteria"`, `color{Violet}"fungi"` and `color{Violet}"cyanobacteria"`.

● You have studied about the `color{Violet}"nodules"` on the roots of `color{Violet}"leguminous plants"` formed by the symbiotic association of `color{Violet}"Rhizobium"`.

● These bacteria `color{Violet}"fix atmospheric nitrogen"` into organic forms, which is used by the plant as `color{Violet}"nutrient"`.

● Other bacteria can `color{Violet}"fix atmospheric nitrogen"` while free-living in the soil (examples `color{Violet}"𝘈𝘻𝘰𝘴𝘱𝘪𝘳𝘪𝘭𝘭𝘶𝘮"` and `color{Violet}"𝘈𝘻𝘰𝘵𝘰𝘣𝘢𝘤𝘵𝘦𝘳"`), thus enriching the nitrogen content of the soil.

● Fungi are also known to form `color{Violet}"symbiotic associations"` with plants (`color{Violet}"mycorrhiza"`).

● Many members of the genus `color{Violet}"Glomus form mycorrhiza"`.

● The `color{Violet}"fungal symbiont"` in these associations `color{Violet}"absorbs phosphorus"` from soil and passes it to the plant.

● Plants having such `color{Violet}"associations"` show other benefits also, such as resistance to `color{Violet}"root-borne pathogens"`, tolerance to `color{Violet}"salinity and drought"`, and an overall increase in `color{Violet}"plant growth and development"`.

● `color{Violet}"Cyanobacteria"` are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. `color{Violet}"𝘈𝘯𝘢𝘣𝘢𝘦𝘯𝘢, 𝘕𝘰𝘴𝘵𝘰𝘤"`, `color{Violet}"𝘖𝘴𝘤𝘪𝘭𝘭𝘢𝘵𝘰𝘳𝘪𝘢,"` etc.

● In `color{Violet}"paddy fields"`, cyanobacteria serve as an important `color{Violet}"biofertiliser"`.

● `color{Violet}"Blue green algae"` also add organic matter to the soil and `color{Violet}"increase its fertility"`.

● Currently, in our country, a number of `color{Violet}"biofertilisers are available commercially"` in the market and farmers use these regularly in their fields to `color{Violet}"replenish soil nutrients"` and to reduce dependence on `color{Violet}"chemical fertilisers"`.